I’ve got a steel road bike which I love, but it develops a speed wobble when descending over about 35mph. It seems to be initiated by crosswinds or braking. What causes it and what can I do about it? Is it caused by brakes touching one side of the rim before another or using one brake over another? Would changing to OS bars and stem help? Or is it all mental and should I just man up?
Thanks!

Worn headset?

Wobbly wheels?

Shimmy?

what can I do about it

Try gripping the top tube with your knees and see if that helps.

And keep the pedals level.

Have you got you weight balanced? I found that coming from MTB I had a tendency to shift my weight too far back, getting back off the saddle – you need to get a bit more weight over the front on a road bike.

This?

It’s related to harmonic motion iirc. Gripping top tube with knees/hand helps, braking can actually make it worse. It can be quite scary, first time it happened to me I thought the wheels were about to fall off.

Descending in a crosswind is something I do NOT enjoy. Scares the crap out of me to be honest. I sit up and take it easy rather than get on the drops.

try changing air pressure in the front a bit.
asides from checking hs/hub bearings

Thanks for the ideas everyone.

Slow down a bit? Sometimes it’s the most obvious. 😐

I’m already the slowest downhill!

Oh, OK. Have a look here for ideas then. 😛